BETA-I,3-GLUCAN HYDROLASES FROM EUGLENA GRACILIS .I. NATURE OF HYDROLASES

1. 1. Cell-freee extracts prepared from Euglena gracilis rapidly hydrolyse a number of β-1,3-glucans as well as show slight, but significant, hydrolytic action on a number of other glucan, glucose oligosaccharides and glucosides. 2. 2. The nature of the enzymes hydrolysing the β-1,3-glucans has been examined. Glucose was the sole product detected during the hydrolysis of paramylon and pachyman and during the early stages of the hydrolysis of laminarin. The hydrolysis of laminarin and paramylon could be substantially blocked by chemical modification of both nonreducing and reducing glycosyl residues but not by modification of reducing residues alone. These observations are consistent with the presence of an exo-hydrolose (β-1,3-glucan glucohydrolase) cleaving terminal, nonreducing glucose residues from these substrates. 3. 3. The extracts also reduced the viscosity of carboxymethylpachyman solutions indicating the presence of an endohydrolase (β-1,3-glucan glucano-hydrolase). Extracts showing little or no endo-hydrolase activity could be obtained by breaking the cells at pH 4.5 rather than pH 5.2, or by heating at 55°. Under both these conditions the exo-hydrolase retained most of its activity. 4. 4. In extracts centrifuged at 9000 × g for 30 min, the exohydrolase was present mainly in the supernatant fraction. Variable amounts of the endo-hydrolase (15-39%) were found associated with the washed pellet which consisted largely of paramylon granules. © 1969.